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20 Threads found on edaboard.com: Cmfb Test
Dear All, I have designed a fully differential operational amplifier with Continuous time common mode feedback circuit. Now I want to check if the cmfb circuit is stable or not. I already tested my operational amplifier in differential mode and it is stable using the AC analysis. Can anyone please tell me how can I test my (...)
Why and how is the second apmlifier ''acOpenDiff'' added? 1. To not load the output of the 1st amplifier additionally 2. To compensate for the DC-amplified offset how is shown on the schematic. Also please explain why is voltage sources at output of fir
i design a 2 stage fully differential opamp. the cmfb of the first stage is continuous-time cmfb and the second stage is the SC cmfb. the problem is:i dont know how to simulate its SR,settling time,ac etc. thanks for you help. Added after 3 minutes: or you can give me
Hi, I want to test the GBW of cmfb in this OTA, but don't know where to separate the circuit and give the input or test the output. Can anybody tell me please? Thanks a lot:)
Are these steps also relevant to an SC cmfb circuit where Vcmo terminal of an ideal op amp is being set by an SC cmfb circuit??
Hello, all The schematic is a fully differential opamp and an ideal cmfb is used and biased @ half VDD. VDD is 3V. I was wondering if it is natural or right to test that or any opamp with a differential voltage which ranges from -1v to 1v because I observed the gain is around 240. The following spice deck is how I test it and check the (...)
I think if you are using the two stage amplification in the cmfb amplifier, the same problem of two stage Opamp stability problems are appearing in your circuit. May be your test bench could be missing some capacitances required. Connecting the two differential outputs with two identical capacitors to the cmfb node may solve the problem and (...)
How can you test the frequency response of a cmfb circuit whose input and output are the same like this circuit which appears in
for a full differential gain-boosted opamp,which parameters should be tested?such as gain,PM,GBW(main opamp \ gain-boost opamp \ cmfb circuit),PSRR,CMRR,offset and so on.any other needed? besides,another question,how to test the above parameters,especially for PSRR,CMRR , offset and any other important parameters? are there some related (...)
i have designed a folded cascode fully differential opamp used for pipelined adc(1.5 bit per stage),but there are some problems: when i test it in open loop with ideal cmfb(vcvs source),the GBW is 103M,dc gain is 80 db,-3db bandwidth is about 10khz;however,when i test it in closed loop with sc-cmfb,there are some strange (...)
My problem is it,s stability. How can i test it? and What is my considerations in my design for stability. Do you Have any simple structure (or full designed) for cmfb design in subthreshold?
I have designed a Fully Differential Amplifier (FDA) with Switched Capacitance cmfb, which is used in pipelined ADC, but I wonder how to simulate the settling time of it. It is different from the OTA with continuous time cmfb because it's working in discrete time or just one half of the period. I have read some materials and have already done
in loop gain in the fully differentail opm with continue cmfb, can we also ues "probe" to test the loop gain? thank u @@
I have search the similar topic in EDAboard but I just get the way to simulate it in Hspice. But in my lab we use cadence as simulation tools so I want to know the way which can be used in Cadence. 3x!
I observed that my cmfb circuit is limiting my amps output swing when compared to the circuit without cmfb. Does cmfb circuit really limit the output swing while forcing a common mode output at the differential output stages?? One more doubt I have is how to test the pulse response of a fully differential amplifier. One (...)
I design a fully differential opm with cmfb. when the offset is good, the linearity is bad; when the linearity is good, the offset is bad. How can statisfy both linearity and offset. Please thanks
Can anyone upload any paper that explains how to test a cmfb loop? Thanks,
Hi, I am designing a cmfb circuit for a folded cascode amplifier in Spectre. When I do the cmfb stability test, I get one pole-zero doublet at some intermediate node. (that zero is left half plane zero) My feeling is that diode connected transistor in cmfb circuit is giving the doublet. But I am not able to understand (...)
Hi, guys I had build a opamp with continuous time cmfb, I want to know the stablity of the loop, ie the GBW, phase margin etc. But I don't know how to simulate it with Hspice! Wish your help~ Best Regards, wdd
Hi all: I designed a full differential opa shown in the file opa.jpg, and I designed a cmfb circuit shown in the file cmfb.jpg too. Though I have already analyse the AC character of this opa, I do not know how to test the stability of the cmfb circuit, who can help me? thanx!!!